Telephone-exchange system



C. L. GOODRUM TELEPHONE EXCHANGE SYSTEM Filed Nov. 26.

Patented 0ct. 30, 1923.

cHanLnsL. GQODRUM, or New ironia,v N.

nfasieaearo Warmwasser-ERIC' ,CoM-

PANY, INCORPORATED, or New Yon-K, N.` 4.eccaricati IoN or New, renin;

Tn'L'nrHoNE-nxcnnnen ,sysanim Application filed November To all whom t 'may concern.

v Be it known that I, CHARLES L. GOODRUM, a citizen of the United States, residingat New York, in the county ofY New Yborln State of New York, have invented certain new and useful Improvements inTelephone- Exchange Systems, of which'the following is a full, clear, concise, and exact. description. Y i

This invention relates to telephone exchange syste-ins and particular y to systems in which in yens is provided for giving supervision of talking connections established through the agency of machine switching apparatus. f

` rlhere exists a. wide variation in the A'different types of talking connections that may be established between subscribers lines in an exchange system. This isfespecially true in the case of an exchange comprising` a plurality ot central otces'lo'ca-ted at various distances troni each other. Certain connections may be for the purpose of uniting a calling' subscriber-s linel with a called subscribers line in the Vsaine central otlice. @ther connections may be extended to subscribers lines in an adjoining oiifice, wnile still'others may lead over interottice trunks through a plurality of ofces inthe system to a distant point. These different classes of connections often provide a convenient andlogical standard on which to base the rates of assessment made against the telephone subscritbers `for the service renderedl Forexainple, subscribers wiliv be permitted to make calls towlines localto their own oliice and also perhaps to nearby ottices, where only short trunks are necessary, tor the iixedtlat rat-e 'of charge.' On distant calls, however, involving the use of long and expensive trunk line-s, an additional assessment is made againstl the'rcalling suibscribers line for each such connection he establishes.

' Where certain olfices are provided with grivate branch exchanges it 'is desirable to give the subscribers to these exchanges the saine privileges Aas* the subscribers'to central cnice lines in obtaining the various classes or connections abovenenuinerated. lt the private branch exchange is one that is 2e, 1920.- seriai 110.426,48?.

equipped with Ina-chine switching apparatus for extending calls to" the central otticefit becomesn'ecessary to provide some means for notifying an operator or attendant in the branch With theforegoing conditions in mind it is the object 'of this invention'to provide, in a system where connections are establish- 'ed over' multi-position selective switches,

ineans for causing the actuation of a signal devi`Ce,when-' oneot' said switches is lselectively operated to certain of its positions, to givel a notification of the class of the callV that is bein'gextended.V f

` A feature of thefinvention relates to the provision of means forl actuating afsign'al device when one of the selective switches 'sedinthe'extension 'of a connection Vis operated 'toJselec-t certainonesof a plurality of groups of outgoing trunks.`

A further feature relates 'to the provision ofy a. signal lamp yat anoperators or attend- 'a'ntsV position which is lighted, Awhen 'one ofthe selective switches isoperated to select certain ones Yof a' plurality of groups of trunks, toadvise Vthe'o'perator of the nature ofthe call' 'thatl is being extended.

@ther teaturesfwill 'appear `from the detailed "description "given hereina't'ter andV from theappefnded claims.`

`Referring fto'the drawing which forms a part' of this application, the 'figure illustrates aportion of atelephone exchange 'system showing in ysuliicient detail the cir'- cufits and apparatus' constituting the subject "niatter'ot the invention. To the left of the vertical broken line in the figure is shown a subscribers telephone line terminating in the niultiples of an automatic switch iria private branch exchange.v Furthermore, certain of the `automatic switches in Jthe private branch exchange are' illustrated Vdiagraniinatically together with one. of the trunk circuits outgoing to the central oliice. To the right of thefvertical line'the central office is shown provided'with van Vautomatic ,selector switchv in which terminates the V,trunk line incoming trom the' private branch mange.-

The antenati@ Switches shown da-gramexchange ofthe class of the call loel matically in the private branch exchange may be of any desired character, but are preferably twomovement step-by-step switches of the well-known type. The automatic selective switches installed at the central ollice, the circuit diagram of one of these switches being shown in detail vin the figure, may likewise be step-by-step switches of any suitable and approved type. The particular switch shown in this disclosure is of the so called around and up type. 1n the primary movement of the switch the brush shaft is rotated to position one of a plurality of sets of brushes in operative relation to a desired group of terminals. In the second movement of the switch the brush shaft is stepped vertically to drive the selected set of brushes over the terminals of the contact bank. The structural details of such a switch are illustrated and explained-in full in the patent to Forsberg, No. 1,252fl20, issued January 8, 1918.

The subscribers to the private branch exchange are afforded the privilege of making ,p calls to lines local to their own central oiiice and also to distant subscribers lines which must be reached by means of interoflice trunk connections. Whatever class of call the private branch exchange subscriber wishes to make, he first extends his line automatically, by means of a dial such as shown at 101, through a selector switch at the private branch exchange which selects an idle trunk 121, 122 outgoing to the cen- ?f tral office. The connection having been extended to an incoming switch at the central office, the next digit or digits will determine the positioning of the switchfor switches in the central office to .route the call either to a local subscribers line or to an interottice trunk, as the case may be. In the case of a local call the first group selector in the central office will be operated to select the proper one of a plurality -of groups of trunks, such as the group illustrated at 150. An idle trunk is then selected in this V.group and the extension of the connection continued to select a called subscribers line. On an interoiiice call, however, the first group selector will be operated to choose the proper one of a plurality of different groups of trunks, one of which groups is illustrated at 140. The hunting movement of the switch thereafter chooses an idle trunk in this group and the connection is extended to the'distant office.

The detailed operation involved in the establishment of the connection will next be considered. For this purpose assume that the subscriber at substation 100 in the private branch exchange wishes to obtain Va connection with a subscribers line local to the central oflice illustrated at the right of the figure. Gn removing the receiver from the swit-chhook at substation 100 an lswitch arm 123 .not become energized at this time.

after the calling subscriber manipulates his impulse transmitter 101 to send a series of impulses corresponding to the first digit in the wanted number. This series of impulses causes the primary operation of the first selector switch, the brushes of which are shown at 108, 109 and 110. Following the group selecting movement of the first selector switch the brushes 108, 109 and 110 are driven automatically to search and make connection with the terminals 111, 112 and 113 of an idle trunk 121 and 122 outgoing to the central otlice.

The following circuit may now be traced for the energization of the line relay 115 associated with the outgoing trunk: Battery, right-hand winding of said relay, lower left-hand winding of repeating coil 114, terminal 112, brush 109, brush 106, terminal 103, through the loop of the calling substation 100,terminal 102, brush 105, brush 108, terminal 111, upper left-hand winding of repeating coil 111, left-hand winding of relay 115 to ground. Relay 115 becomes en- 124 (position 1), conductor 122, lower righthand winding of repeating coil 1111, contact and right-hand armature of relay 115, winding of relay 120, upper right-hand winding of repeating coil 114;, conductor 121, side (position 1), left-hand winding of relay 125 to ground. 1t may be noted that the instant that the relay 115 attracts its armature a circuit is momentarily closed from battery through the Winding of relay 118, right-hand normal contact of said relay, armature and contact of relay 117, contact and armature of relay 120, front cntact and left-hand armature of relay to ground. Relay 118 is constructed to attract its armatures slowly, and, therefore before it can become energized the relay operates in series with relay to open the circuit just traced for relay 118. Relay 118 consequently'does Relay 116, at its right-hand armature and contact, closes a circuit for the application of ground potential to the test terminal 113 of the outgoing trunk in order to render this trunk non-selectable to other switches in the private branch exchange.

When relay 125 operates it completes a circuit from battery through the winding of relay 126, front contact and armature of relay 125 to ground. Relay 126 becomes operated in this circuit and prepares a circuit for the primar f stepping magnet 129. The calling subscri er, opera-ting his impulse transmitter 1O1,.sendsl out a series or' impulses corresponding to `the next digit of the called number. On the irst interruption of the line circuit relay 115 releases its armatures and opens the circuit of relay 116. This relay, however, being slow-torelease does not deenergize in the briefinterruptions of Vits circuitduring the transmission o'f a series of impulses. Relay 115 closes a circuit :trom round through its left-hand armature ancback contact, letthand armature and contact of relay 116, winding of relay 117, to battery and ground. Relay 117 becomes energized and being of the slow-to-release character remains operated during the following impulses of the series. Relay 117, at its armature and con` tact, maintains open the operating circuit of relay 118. i

Relay 115, at its right-hand armature and contact, opens the circuit of relay 120 and Jthe impulse relay 125 atthe central oiiice. Relay 125, on deenergizing, completes a circuit from ground through its armature and back contact, lett-hand armature and contact ot relay 126, ofi" normal contact 154, winding of primary stepping kmagnet 129, to battery and ground. ln parallel thereto a circuit is also completed through the winding ot the slow-to-release relay 127 to bat tery and ground. Relay 127, at its arma` ture and Contact, closes a circuit for the energiza-tion of the escape magnet 128. The escape magnet 128 operates and prepares to release the side switch into position 2 when the energizing circuit of said magnet is opened. The primary stepping magnet 129 operates to advance the set of brushes 133, 134 and 135 through one rotary step. Then the line circuit closes at the end of the irst impulse relay 115 attracts its armatures and completes the energizing circuit for relays 125 and 120. Relay 125 opens the circuit et stepping magnet 129 and relay 127 and recloses the circuit Yoi" slow-torelease relay 126. Relay 127 remains energized While the stepping magnet 129 releases its armature. li'vhen relay 126 first energizes it completes a circuit from battery through the winding et relay 132, contact and right-hand armature of relay 126 to ground. Relay 132 becomes energized and remains energized as long as relay 126 holds its armaturesvattracted.

For each succeeding impulse ofthe series the magnet 129 drives the set of brushes through one rotary step lfinally. bringing them to rest in operative relation' to the group of trunks 150.containing the trunk 151, 152 an-d 153. During the primary roy tary movement of the switch, the group brush 142, attached to the brush shaft, is rotated from one segment to another. VThe brush 142 is so attached to the brush shaft as to participate inthe rotary movement 1 it was assumed that the call being extended'V was one for a local subscribers line, the group brush 142 kat the end of themovement of the switch is standing on some one of the group terminals other than terminals 143, 144 and 145, which are shown connected to the conductor 155. v

After an interval has elapsed following the transmission of the last impulse', relay 125 remains energized long enough tol permit the release oit slow relay 127. Relay 127 opens the circuit of the escape magnet 128 which immediately deenergizes and advances the brushes 123, 124, 141, 146, 149 and 157 of the side switch to their second position terminals. 1n this position of the side switch the escape magnet 128 is iinmediately energized in a circuit from battery through the winding of said magnet, arm 146 (position 2), oit normal contact 147 to ground. VMagnet 128 operates preparatory to releasing the side switch into its third position upon denergization. Also a `circuit is established from battery through the winding and contact and armature of the secondary stepping magnet 130, arm 149 (position 2), front Contact and armature of relay 125 to ground. The stepping magnet 130 energizes, interrupts its own circuit and advances the brushes 133, 134, and 135 on tot,y the first set of terminals'in the selected group 150. .As the brush shaft takesV its iirst vertical step the ott normal contacts 147 and 154 are opened. Contact 147, however, does not open until shortly after the test brush 135 has made engagement with the test terminal ot the irst trunk. Hence, if the first trunk in the group is busy a ground potential will be present on the test terminal 153 and a circuit is completed as follows for maintaining the energization of the escape magnet 128: Battery, through the winding of said magnet, arm 146 (position 2) test brush 135 to the grounded test terminal 153. The side switch remains in position 2 and the stepping magnet 130 continues to advance the brushes until the `irst idle trunk in the group is reached. At this time the escape'magnet 128 becomes deenergized and advances the side switch from itsy second to its third position. "Side switch arm 149in leaving position 2 opens the cirtain the trunk busy and also to cuit of the stepping magnet 130 to prevent any further operation of the switch. The test terminal 153 is immediately rendered busy to prevent selection by other switches by means ot the `tollowing circuit: Ground through the right-hand armature and contact ot relay 126, side switch arm 15"( (position 3), side switch arm 146 (position 3), brush 135 to the multiples of terminal 153.

The side switch on passing out of position 2 opens, at its arms 123 and 124, the circuit including the rinding et relay 125 and relay 120 in the private branch exchange. These rela 7s immediately become deenergized. ritter an interval has elapsed the slow-to-release relay 126 also releases its armatures. The release of relay 126 removes the ground, which up to this time has atiorded a holding circuit tor relay 132 and also served to render the test terminal 153 of the selected trunk temporarily busy. Befiore the relay has had time to deenergine, however, a ground potential is supplied from the succeeding switch to mainhold the relay 132 energized. The manner in which this ground potential is applied to the` test terminal 153 'from the succeeding' switch before the slow-to-release relay 126 has had time to deenergize is shown and described in the patent to Clausen, No. 1,340,933, issued May 25, 1920.

From this point on the extension of the call is continued under the control of the calling subscriber, and as many succeeding switches are operated as are necessary to eX- tend connection to the called subscribers line.

At the termination et the conversation the called subscriber', by replacing his receiver on the switchhook, brings about the release, in any well-known manner, ot the switches succeeding those shown in the drawing. The release or" the next succeeding switch causes the removal ot ground potential roin the test terminal 153 and the resultant oeenergization of relay 132. The release ol" relay 132 causes the closure of a circuit from battery through the winding of release magnet 131, primary oli normal contact 148 Contact and armature ot relay 132 to ground. Magnet 131 energizes and locks up in circuit through its Contact and armature and the off normal contact 143. The brushes 133, 134, and 135 are restored to their normal position which time the contact is opened and the release magnet 131 becomes deenergized. The callingsubscriber, by replacing his receiver to the switchhook, brings Vabout the release ot the automatic switches in the private branch eX- change.

A case will next be considered in which a. subscriber in the private branch exchange wishes to obtain a connection with a subscribers line ina distant office, necessitating the use ot an interoftice trunk interconnecting such distant oiiice with the central otlice illustrated in the drawing. rlhe operation of the apparatus in the private branch exchange takes place in the manner already described. instrumental in the group selecting movement ot the automatic switch in the central oiiice differs in the present case, however,

`from the corresponding digit of the number previously considered. rIhe result is that the brush shaft oit the selector switch carrying .the brushes 133, 134 and 135 is rotated to selectone ot a plurality of groups of trunks, such as the group 140, leading to the desired distant oliice. As shown, the selector switch is equipped with three such groups of trunks which correspond to the group terminals 145, 144 and 143. Obviously, as many interotlice trunk groups as desirable could be provided.

Since the brushes 133, 134 and 135 at the end of the primary increment of the switch are standing in operative relation to a group of interoiice trunks leading to a distant ot'- ice, the group brush 142 is in engagement with one o1" the groups of terminals, such as terminal 145, connected to the conductor 155. Therefore, when the slow-to-releasc relay 12T becomes deenergized, following the series ot impulses, and the escape magnet 128 operates to advance the side switch into the second position, a circuit is closed as follows to shunt out the relay 120 at the private branch exchange: Battery through the right-hand winding oi relay 125, conductor 155, terminal 145. brush 142, side switch arm 141 (position 2) left-hand winding of relay 125 to ground. Relay 120 in the private branch exchange deenergizes and completes a circuit from battery through the winding and normal contact of relay 118, armature and contact of relay 117, contact and armature oi' relay 120, front contact and lett-hand armature ot relay 115 to ground. lt will be noted that the slow-to-release relay 117 becomes deencrgized following the lapse of the necessary interval after the transmission oia the series ot impulses. rl`he relay 118 operates and closes a holding circuit `tor itself from battery through its winding, make before break Contact and right-hand armature to ground at the contact and right-hand armature of relay 116. Relay 118, at its lett-hand armature, closes a circuit for the signal lamp 119. The attendant at the private branch exchange, observing the illumination ot the lamp at 119, knows that some subscriber is making a central ofiice call of the class that requires an additional charge. She thereupon depresses her listening key 159 which places her head set in talkingl relation with the calling line. By inquiring The digit of the called number from `the calling subscriber the attendant learns of the nature ot the call being extended and thereby deteimines the necessary charge to be made against the calling line in case the desired call proves successful. After having learned all the-necessary information for determining the additional charge to be made, the attendant releases listening key 159 and retires from the connection.

Returning to the point where the group selector in the central oiice had completed its group selecting movement and t-he escape magnet had released the side switch into the second position, it may be noted that from here on the extension of the connection progresses in the manne-r similar to that described in detail hereinbefore. The circuit ot the secondary magnet 130 is closed and the brushes 133, 134 and 135 are elevated vertically to select an idle trunk 136, 137 and 138 in the interoce group 140. The brush shaft takes its first secondary step immediately that the side switch reaches position 2, but since the brush 142 does not disengage the -terminal 145 during the vertical movement of the switch the shunt around the winding of relay 120 is maintained for a period to insure the operation ot the slow to energize relay 118 in the private branch exchange. After an idle trunk has been found the side switch advances into position 3 and the circuit of relay 125 is opened as arm 141 leaves its second position terminal. From this point on the further extension and release of theinteroiiice connection may take place in any well-known manner.

IVhat is claimed is: Y

1. In a telephone exchange system, a connecting circuit, a multi-position 'selective switch having primary and secondary movements, means for extending a talking connection over said circuit to the selective switch, means for operating said switch to any one of its positions, a signal, actuating means controlled over said connecting circuit for actuating said signal, and means operated when the selective switch is moved to certain of its posit-ions for rendering said actuating means effective. v

2. In a telephone exchange system, an office. a second otiice, a. trunk circuit interconnect-ing said oiiices, a multi-position select-ive switch at the second oiiice, means for extending a talking connection over said trunk to the selective switch in the second otiice, means tor operating said switch to any of its positions. a. signal in said rst oiiice, means controlled over said trunk circuit for actuating said signal, and means operated when the selective switch is moved to certain of its positions tor rendering said actuating means eii'ective. Y

3. In a telephone exchange system, an oitice, a second office, a two-'wire trunk circuit Vtrunk -to the selective switch in thesecond office, means for operating said switch to any of its positions, a signal'in said rst office,

means controlled over said trunk circuit forI actuating said signal, and means operated when the selective switch is moved to certain of its positions for rendering said actuating means effective.

4. In a telephone exchange system, a trunk circuit, a multi-position selective switch having primary and secondary movements, means for extending a talking connection over said trunk to the selective switch, means for operating said switch to any one of its posit-ions, a signal, means operated when said switch is moved to certain of its positions for changing the electrical condition ot said trunk, and means responsive to said change for actuating said signal.

5. In a telephone exchange system, a connecting circuit, a multi-position selective switch lhaving primary and secondary movements, means for extending a talking conneotion Y over said circuit to the selective' switch, a plurality ot groups of trunks to which said switch hasaccess, means for operating said switch to select any one of said groups of trunks, a signa-l, means controlled over said connecting circuit for actuating said signal, and means operated when said switch is moved to select certain ofsaid groups of trunks for rendering said actuating means eiective.

6. In a telephone exchange system, an office, a second otiice, a trunk circuit interconneet-ing said offices, a multi-position selective switch in said second oiiice, means for extending a connection over the trunk circuit to said switch, means for operating said switch to any onenoii? its positions` an operators position at the first oflice, a signal lamp at the operators position, means operated when the selective switch is moved to certain of its positions for changing the electrical condition off said trunk at said secondV ollice` and means at the first oflice responsive to such change in condition Jfor rendering the signal lamp at the operato-rs position et'- feet-ive.

7. In a. telephone system, a private branch exchange, a main office, a trunk circuit terminating at one end in said private branch exchange and at its other end insa-id main oiiice, a. signal for said trunk at the private `branch exchange, an operators telephone set thereat, a selector associated with said trunk at the main oiiice, groups of trunks terminating in said selector and leading to dis- `tant and local ofiices, a subscribers line at said priva-te branch exchange, a sender thereat, a switchcontrolled thereby for extend- Y ing the subsorbers line to said trunk and telephone set With the trunk to supervise the for then operating the said selector to seconnection. lect a, group of said trunks, means operated In Witness whereof hereunto subscribe 10 only when a trunk group to a distant office my name this 20th day of November, A. D., 5 is selected for operating said signal, and 1920.

means controlled by the operator at the pr vate brunch exchange for connecting her CHARLES L. GOODRUB/L 

